Even though embodiments of the invention will be described herein in relation to a TD-SCDMA (Time Division-Synchronous Code Division Multiple Access) system, it should be noted that embodiments of the invention may be equally applicable in other scenarios. Thus, the invention is not limited to TD-SCDMA.
A channel in a mobile communication system is typically complex and time-variable. The channel may be estimated and measured at a receiver and then a coherent detection may be performed on a received signal according to a channel estimation (simply referred as “CHE”). Besides in signal detection, the channel estimation may also play a very important role in physical layer measurement, intelligent antenna and radio resource management, and so forth.
FIG. 1 is a schematic diagram showing a structure of a burst signal in a service slot of a TD-SCDMA system. As shown in FIG. 1, in a TD-SCDMA system, a Midamble code in the middle of the burst signal is for channel estimation, which is also referred as a training sequence. Data on both ends of the Midamble code are for transmitting service data. Both the training sequence and the service data are transmitted by a time division method, and slots of different cells are synchronous.
In a TD-SCDMA system, for an intra-frequency network (FRF=1), a conventional channel estimation method mainly includes: obtaining a coarse channel estimation of each cell by a single cell channel estimation algorithm, according to a received Midamble code and basic Midamble codes of every cell; performing an interference cancellation on the coarse channel estimation with iteration; and performing a denoise processing on the channel estimation after the interference cancellation.
In the conventional method, a number of times of iteration is fixed. Since a channel environment of a UE may vary at any given time, the number of times of iteration is usually set to a large value in order to adapt to different channel environments. Therefore, for certain channel environments, if the number of times of iteration is too large, “over-cancellation” may occur, i.e., there may be a case where an interference cancellation is performed on a signal path using a noise path, which leads to inaccurate channel estimation.
Therefore, the conventional channel estimation method needs to be further improved so as to overcome the above weakness.